From a page move: This is a redirect from a page that has been moved (renamed). This page was kept as a redirect to avoid breaking links, both internal and external, that may have been made to the old page name.
To a monotypic taxon: This is a redirect from the only lower-ranking member of a monotypic mammal taxon to its monotypic taxon. In a biology-related article, when for example a genus has only one species, the binomial name may be a redirect to the genus.
Use {{R from monotypic taxon}} instead when making a redirect from a monotypic taxon to its only member, for example, from a family name to its sole genus.